diff --git a/common/util/src/main/java/com/antgroup/openspg/common/util/CommonUtils.java b/common/util/src/main/java/com/antgroup/openspg/common/util/CommonUtils.java
index 8d35a83ae..774fd046c 100644
--- a/common/util/src/main/java/com/antgroup/openspg/common/util/CommonUtils.java
+++ b/common/util/src/main/java/com/antgroup/openspg/common/util/CommonUtils.java
@@ -271,9 +271,10 @@ public static void getScannerReaderConfig(
     if (reader == null) {
       reader = new JSONObject();
     }
-    JSONObject builderExtension = JSON.parseObject(job.getExtension());
+    JSONObject builderExtension =
+        job == null ? new JSONObject() : JSON.parseObject(job.getExtension());
     JSONObject llm = JSONObject.parseObject(project.getConfig()).getJSONObject(CommonConstants.LLM);
-    String dataSourceType = job.getDataSourceType();
+    String dataSourceType = job == null ? null : job.getDataSourceType();
 
     if (BuilderConstant.YU_QUE.equalsIgnoreCase(dataSourceType)) {
       scanner.put(BuilderConstant.TYPE, BuilderConstant.YU_QUE);
@@ -420,6 +421,9 @@ public static void getScannerReaderConfig(
   }
 
   public static String getKagBuilderInput(BuilderJob builderJob, Date bizDate) {
+    if (builderJob == null) {
+      return "";
+    }
     String input = builderJob.getFileUrl();
     String dataSourceType = builderJob.getDataSourceType().toLowerCase();
     if (BuilderConstant.ODPS.equalsIgnoreCase(dataSourceType)) {
diff --git a/server/api/http-server/src/main/java/com/antgroup/openspg/server/api/http/server/openapi/BuilderController.java b/server/api/http-server/src/main/java/com/antgroup/openspg/server/api/http/server/openapi/BuilderController.java
index f0e3754bd..eef66359f 100644
--- a/server/api/http-server/src/main/java/com/antgroup/openspg/server/api/http/server/openapi/BuilderController.java
+++ b/server/api/http-server/src/main/java/com/antgroup/openspg/server/api/http/server/openapi/BuilderController.java
@@ -128,7 +128,18 @@ public void check() {
 
           @Override
           public Boolean action() {
-            return builderJobService.deleteById(id) > 0;
+            BuilderJob builderJob = builderJobService.getById(id);
+            if (builderJob == null) {
+              return Boolean.FALSE;
+            }
+            boolean deleted = builderJobService.deleteById(id) > 0;
+            // Tear down the linked scheduler job so its DAG instances do not keep
+            // executing sync tasks against a BuilderJob that no longer exists.
+            // Otherwise reader/retrieval sync tasks dereference a null BuilderJob (see #732).
+            if (deleted && builderJob.getTaskId() != null) {
+              schedulerService.deleteJob(builderJob.getTaskId());
+            }
+            return deleted;
           }
         });
   }
diff --git a/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/KagReaderSyncTask.java b/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/KagReaderSyncTask.java
index 010b0e6c4..37d3db4f2 100644
--- a/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/KagReaderSyncTask.java
+++ b/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/KagReaderSyncTask.java
@@ -48,6 +48,10 @@ public class KagReaderSyncTask extends SyncTaskExecuteTemplate {
   public SchedulerEnum.TaskStatus submit(TaskExecuteContext context) {
     SchedulerJob job = context.getJob();
     BuilderJob builderJob = builderJobService.getById(Long.valueOf(job.getInvokerId()));
+    if (builderJob == null) {
+      context.addTraceLog("builderJob %s not found, skip reader", job.getInvokerId());
+      return SchedulerEnum.TaskStatus.FINISH;
+    }
     List<ChunkRecord.Chunk> chunks = readSource(context, builderJob);
     SchedulerTask task = context.getTask();
     String fileKey =
diff --git a/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/RetrievalSyncTask.java b/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/RetrievalSyncTask.java
index 41279dc68..4adc78b29 100644
--- a/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/RetrievalSyncTask.java
+++ b/server/core/scheduler/service/src/main/java/com/antgroup/openspg/server/core/scheduler/service/task/sync/builder/RetrievalSyncTask.java
@@ -69,6 +69,10 @@ public SchedulerEnum.TaskStatus submit(TaskExecuteContext context) {
 
     SchedulerJob job = context.getJob();
     BuilderJob builderJob = builderJobService.getById(Long.valueOf(job.getInvokerId()));
+    if (builderJob == null) {
+      context.addTraceLog("builderJob %s not found, skip retrieval", job.getInvokerId());
+      return SchedulerEnum.TaskStatus.FINISH;
+    }
     String retrievals = builderJob.getRetrievals();
     if (StringUtils.isBlank(retrievals)) {
       context.addTraceLog("index not set");
@@ -79,6 +83,10 @@ public SchedulerEnum.TaskStatus submit(TaskExecuteContext context) {
     Project project = projectService.queryById(job.getProjectId());
     for (Long id : retrievalList) {
       Retrieval retrieval = retrievalService.getById(id);
+      if (retrieval == null) {
+        context.addTraceLog("retrieval %s not found, skip", id);
+        continue;
+      }
       context.addTraceLog("update index(%s) schema", retrieval.getName());
       String schemaDesc = retrieval.getSchemaDesc();
       if (StringUtils.isBlank(schemaDesc)) {